As described in applicant's co-pending patent application Ser. No. 485,983 which was filed July 5, 1974, now U.S. Pat. No. 4,023,456 a system for encoding music is disclosed. The apparatus which is shown in that application is used in encoding and decoding a keyboard instrument. It forms electrical signals readily recorded for subsequent playback. The apparatus is believed to be quite successful as disclosed.
That disclosure pre-supposes some type of tape recording apparatus or a two wire transmission system. The term "two wire" refers to a transmission system where the band width of the data which is being transferred by the system can be readily placed on a pair of wires and, indeed, they need not be coaxial wires to enable transmission of an extremely wide band width. The band width which is required for the transmission of the musical data modulated in this form is within the audio range of typical commercial grade telephone circuitry, typically a pass band of 0.3 to 3.0 kilohertz.
The present invention is therefore an accessory to that equipment. It enables the data to be transferred over unlimited distances using a two wire carrier system of any desired construction. The apparatus forms a digital signal where the freguency content is less than about three thousand hertz to enable the transmission of keyboard music. The present invention is a unique modulation device. It is particularly unique in that it forms a procession of pulses which can be transferred on open wires without regard to carrier frequency insertion, clock signal, synchronization pulses, and so on. It can be easily recorded on a single channel tape recording apparatus. Substantial loss of quality can be endured without destroying the wave form of the signal to be stored or transferred.